The study will systematically explore the efficacy of EMG biofeedback and operant shaping in overcoming spasticity and related neuromuscular deficits in victims of stroke, accidental brain injury, or cerebral palsy. Subjects will be about 20 spastic hemiplegics from 6 to 60 years old, of stable neurological condition, devoid of other medical or behavioral problems (e.g. athetoid movements, aphasia, hyperactivity) which might interfere with learning. Spastic muscles will be trained in synergist pairs. Each subject will be trained to relax normal and then spastic muscles under quiet resting conditions. He will then be reinforced for using feedback to extend control of spasticity to gradually more challenging stimulus and task conditions. In experiment I, the spastic limb remains at rest while "overflow" conditions such as distracting noise, tactual stimuli, or use of the normal contralateral limb are introduced. In experiment II, the subject strives to relax the spastic muscles during passive stretch produced by passive flexion and extension at increasing isokinetic rates or by an automated reflex hammer suddenly displacing the muscle tendon. In experiment III neuromuscular skills prerequisite to active synergistic use of the spastic limb are trained. Each experiment involves individualized training of 8 or more subjects for about ten 40 to 50 minute daily sessions, allowing subjects to proceed at their own rates in mastering successively more difficult tasks. An on-line computer quantifies and records momentary EMG levels, generates visual feedback displays, carries out response shaping and reinforcement schedules using a monetary incentive, and processes data concurrently.